Hybrid multi-pulse rectifier transformer with active filtering capability and active filtering method thereof
By introducing a multi-winding phase-shifting transformer and an active filter circuit into a multi-pulse rectifier transformer, combined with a thyristor rectifier circuit, active compensation and filtering of harmonic currents is achieved, solving the problem that traditional transformers do not have active filtering capabilities, improving power quality and reducing system complexity and cost.
Patent Information
- Application Number
- CN202511224408.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-29
- Publication Date
- 2026-01-16
AI Technical Summary
Traditional multi-pulse rectifier transformers lack active filtering capabilities, suffer from severe harmonic distortion, and cannot meet the power quality requirements of new power systems. Existing improvement methods increase system complexity and cost.
It adopts a hybrid structure of interconnected multi-winding phase-shifting transformer, active filter circuit, thyristor multi-pulse rectifier circuit and filter winding. It achieves active compensation and filtering of harmonic current by controlling IGBT and DC capacitor. It combines three-phase inverter and filter inductor for filtering. It uses controllable thyristor to control the conduction angle to achieve voltage regulation.
It achieves active filtering function for various power grid application scenarios, reduces harmonic distortion, maintains the robustness and structural simplicity of traditional phase-shifting transformers, and reduces the complexity and cost of power electronic transformers.
Smart Images
Figure CN121356321A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to rectifier transformers, and more particularly to a hybrid multi-pulse rectifier transformer with active filtering capability and its active filtering method. Background Technology
[0002] Multi-pulse rectifier transformers offer advantages such as simple implementation, high reliability, and strong overload capacity, and are widely used as interfaces between electronic equipment and the AC power grid in various fields, including wind turbine generators, ship and tank power supply. However, with the rapid development of energy interconnection and smart grids, electronic equipment is placing higher demands on the reliability, flexibility, and power quality of power supply.
[0003] Traditional phase-shifting transformers, as one of the most important components in multi-pulse rectifier transformers, suffer from problems such as large size, heavy weight, high no-load loss, harmonic distortion, and severe pollution, which can no longer meet the needs of today's rapidly developing technologies. In particular, traditional phase-shifting transformers lack the ability to actively filter and regulate power quality, making them unable to cope with the complex harmonic environment brought about by the integration of various electronic devices in modern power systems. Compared to traditional transformers, hybrid transformers (HDTs) combine power electronic devices with power frequency transformers. They not only possess the high efficiency and reliability advantages of traditional transformers but also significantly improve the controllability of traditional transformers through power electronic devices, providing active filtering and power quality control capabilities. Therefore, they are highly suitable for the development needs of new smart grids.
[0004] Existing improvements to multi-pulse rectifier transformers mostly focus on adding power electronic filter circuits to the primary side or harmonic suppression circuits and pulse multiplier circuits to the output side to improve filtering performance. This approach undoubtedly increases the complexity and cost of the multi-pulse rectifier system. Furthermore, existing technologies such as patent CN117578893A use a three-stage power electronic transformer instead of a phase-shifting transformer and employ PFC circuitry on the primary side for power factor regulation to meet harmonic standards. While this reduces the size of the multi-pulse rectifier, the power electronic transformer is expensive and complex to control, making it unsuitable for widespread adoption. At the same time, power electronic transformers, limited by current device technology, exhibit poorer stability and shorter lifespan compared to traditional transformers. Summary of the Invention
[0005] Purpose of the invention: The purpose of this invention is to provide a hybrid multi-pulse rectifier transformer with a simple structure and active filtering capability, and its active filtering method, in order to solve the problem that traditional multi-pulse rectifier transformers do not have active filtering capability and have serious harmonic distortion that does not meet the standards.
[0006] Technical Solution: The present invention discloses a hybrid multi-pulse rectifier transformer with active filtering capability, comprising: a multi-winding phase-shifting transformer, an active filtering circuit, a first thyristor multi-pulse rectifier circuit, and a second thyristor multi-pulse rectifier circuit connected in series. The primary side of the multi-winding phase-shifting transformer is connected to a three-phase power grid, and the secondary side is connected to two thyristor multi-pulse rectifier circuits and an active filtering circuit. The two thyristor multi-pulse rectifier circuits are used to rectify the AC power supplied by the secondary side of the multi-winding phase-shifting transformer into DC power, providing DC voltage to the load and the active filtering circuit. The multi-winding phase-shifting transformer generates three sets of three-phase voltages. Two sets of three-phase voltages with different phases and the same amplitude generated by phase shifting are output to the two thyristor multi-pulse rectifier circuits respectively. The other set of three-phase voltages is not phase-shifted and is connected to the active filtering circuit. The active filtering circuit inverts the DC voltage into AC current and transmits it to the primary winding for active compensation and filtering of primary harmonic current.
[0007] Optionally, the multi-winding phase-shifting transformer includes three-phase windings. Each phase winding includes a primary winding, a first rectifier winding, a second rectifier winding, and a filter winding. The primary winding is used to connect to a three-phase AC power supply. The first rectifier winding is connected to the input of a first thyristor multi-pulse rectifier circuit on the secondary side. The second rectifier winding is connected to the input of a second thyristor multi-pulse rectifier circuit on the secondary side. The filter winding is connected to the output of an active filter circuit on the secondary side.
[0008] Optionally, the active filtering circuit includes a three-phase inverter composed of diodes, IGBTs, and DC capacitors. The positive outputs of the first and second thyristor multi-pulse rectifier circuits are connected to the positive DC input of the three-phase inverter. The negative DC terminals of the first and second thyristor multi-pulse rectifier circuits are connected to the negative DC terminal of the three-phase inverter. The output of the three-phase inverter is connected to the secondary side of the multi-winding phase-shifting transformer.
[0009] Optionally, the active filtering circuit also includes a three-phase filter inductor disposed between the output terminal of the three-phase inverter and the secondary winding, for filtering the AC current output by the three-phase inverter.
[0010] Optionally, the DC voltage provided by the DC capacitor can be converted into AC current by controlling the IGBT, and the AC current can be filtered by the three-phase filter inductor. The filtered AC current is then transmitted to the primary winding through the secondary winding.
[0011] Optionally, the hybrid multi-pulse rectifier transformer also includes a current-limiting diode. The positive outputs of the first and second thyristor multi-pulse rectifier circuits are connected to the positive DC input of the active filter circuit via the current-limiting diode, and the negative outputs of the first and second thyristor multi-pulse rectifier circuits are connected to the negative DC input of the active filter circuit.
[0012] Optionally, the hybrid multi-pulse rectifier transformer also includes a balancing reactor. The DC current output from the first thyristor multi-pulse rectifier circuit and the second thyristor multi-pulse rectifier circuit is connected in parallel through the balancing reactor to supply power to the load.
[0013] Optionally, if the load can provide a stable DC voltage, by adjusting the control strategy of the active filter circuit, the active filter circuit can also change the current direction on the primary side by outputting current to the primary side, thereby providing reverse power flow support for the power grid.
[0014] Optionally, both the first thyristor multi-pulse rectifier circuit and the second thyristor multi-pulse rectifier circuit are composed of controllable thyristors. By controlling the conduction angle of the thyristors, the thyristors can be switched on and off to achieve multi-pulse rectification and output voltage regulation functions.
[0015] The active filtering method for the hybrid multi-pulse rectifier transformer of the present invention achieves active compensation and filtering of primary side harmonic current by controlling the active filtering circuit, and includes the following steps:
[0016] (1) The primary side three-phase AC current i a i b i c The system is sequentially transformed into a two-phase stationary coordinate system and then into a two-phase rotating coordinate system. The component i of the primary side AC current before low-pass filtering in the two-phase rotating coordinate system is then analyzed. d i q The harmonic components i in the primary AC current are extracted by subtracting the low-pass filtered component. d,h i q,h And its component i in the two-phase stationary coordinate system is obtained by inverse two-phase rotation transformation. α,h i β,h ;
[0017] (2) The AC voltage v output by the active filter circuit a v b v c The system is sequentially transformed to a two-phase stationary coordinate system and then to a two-phase rotating coordinate system. The DC component information (v) in the two-phase rotating coordinate system is then extracted using a low-pass filter. d,dc v q,dc The DC capacitor voltage V dc Its reference value V dcref The difference between them is passed to the PI controller for calculation, and the output of the PI controller is compared with the previously obtained v. d,dc v q,dc Multiplying them together yields the current reference value i corresponding to DC voltage control. rd i rq And its component i in the two-phase stationary coordinate system is obtained by inverse two-phase rotation transformation.rα i rβ ;
[0018] (3) The harmonics of the primary AC current in the two-phase stationary coordinate system obtained in steps (1) and (2) are respectively... α,h i β,h and DC voltage control current reference value i rα i rβ As a reference value for the output current of the active filter circuit, and compared with the output AC current i of the active filter circuit transformed into a two-phase stationary coordinate system. Lα i Lβ The difference is calculated, and the result is multiplied by the filter circuit coefficient to obtain the reference value for the output voltage of the active filter circuit. This reference value is then compared with the output AC voltage V of the active filter circuit in the two-phase stationary coordinate system. α V β The difference is calculated, and the result, after inverse transformation to the three-phase stationary coordinate system, is used as the three-phase modulation voltage v' of the three-phase voltage source rectifier in the active filter circuit. a 、v'b、v' c ;
[0019] (4) Based on the three-phase modulation voltage v' obtained in step (3) a v' b v' c Calculate the zero-sequence voltage and superimpose it with the three-phase modulation voltage to obtain the final three-phase modulation voltage reference value v'. a,ref v'b,ref,v' c,ref Furthermore, the three-phase modulation voltage reference value is controlled by the PWM output to control the three-phase voltage source rectifier, thereby realizing the active filtering function.
[0020] Beneficial effects: Compared with the prior art, the significant technical effects of the present invention are as follows: the active filtering circuit is integrated into the multi-winding phase-shifting transformer in the form of a filtering winding, realizing active filtering of different harmonic currents under various power grid application scenarios; by forming a hybrid transformer with the active filtering circuit and the multi-winding phase-shifting transformer, the proposed multi-pulse rectifier transformer has an active filtering function on the basis of passive filtering, while not requiring the introduction of a power electronic transformer with a more complex structure and control, thus retaining the robustness and simple structure of the traditional phase-shifting transformer. Attached Figure Description
[0021] Figure 1 This is the circuit topology diagram of the hybrid multi-pulse rectifier transformer described in this invention;
[0022] Figure 2 This is a control block diagram of the active filter circuit of the hybrid multi-pulse rectifier transformer described in this invention;
[0023] Figure 3 These are simulation curves of the three-phase primary AC voltage and current, active filter circuit output current, DC capacitor voltage and DC load power before and after applying the hybrid multi-pulse rectifier transformer according to an embodiment of the present invention. Detailed Implementation
[0024] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.
[0025] like Figure 1 As shown, the hybrid multi-pulse rectifier transformer with active filtering capability of the present invention includes: a multi-winding phase-shifting transformer, an active filtering circuit, a first thyristor multi-pulse rectifier circuit, a second thyristor multi-pulse rectifier circuit, a current-limiting diode, and a balancing reactor connected in series. The primary side of the multi-winding phase-shifting transformer is connected to a three-phase power grid, and the secondary side is connected to two thyristor multi-pulse rectifier circuits and an active filtering circuit. The two thyristor multi-pulse rectifier circuits are used to rectify the AC power supplied from the secondary side of the multi-winding phase-shifting transformer into DC power, providing DC voltage to the load and the active filtering circuit. Due to the use of multi-pulse technology, harmonics in the voltage can be reduced.
[0026] The multi-winding phase-shifting transformer has three phase windings, named A-phase, B-phase, and C-phase respectively. Each phase winding includes a primary winding, a first rectifier winding, a second rectifier winding, and a filter winding. The primary winding is used to connect to a three-phase AC power supply. The first rectifier winding is connected to the input of the first thyristor multi-pulse rectifier circuit on the secondary side. The second rectifier winding is connected to the input of the second thyristor multi-pulse rectifier circuit on the secondary side. The filter winding is connected to the output of the active filter circuit on the secondary side.
[0027] The positive output of the first thyristor multi-pulse rectifier circuit is connected to the positive terminal of the balancing reactor, and then connected to the positive DC input of the active filter circuit (i.e., the positive terminal of the DC capacitor) via a current-limiting diode. The positive output of the second thyristor multi-pulse rectifier circuit is connected to the negative terminal of the balancing reactor. The output of the balancing reactor is connected to the positive terminal of the load, and provides DC power to the load through the balancing reactor. The negative DC terminals of the first and second thyristor multi-pulse rectifier circuits are interconnected with the negative DC terminal of the active filter circuit (i.e., the negative terminal of the DC capacitor), and finally connected to the negative terminal of the load.
[0028] The multi-winding phase-shifting transformer is used to receive and phase-shift the three-phase voltage from the power grid, and to transmit the filtered current output by the active filter circuit to the primary side. The multi-winding phase-shifting transformer generates three sets of three-phase voltages. Two sets of three-phase voltages generated by phase shifting, with a phase difference of 30° and the same amplitude, are output to the first thyristor multi-pulse rectifier circuit and the second thyristor multi-pulse rectifier circuit, respectively, through the first rectifier winding and the second rectifier winding. The other set of three-phase voltages is not phase-shifted and is connected to the active filter circuit through the filter winding.
[0029] Both the first and second thyristor multi-pulse rectifier circuits are composed of controllable thyristors. In this embodiment, each circuit consists of two thyristors per phase, for a total of six thyristors across three phases. Multi-pulse rectification and output voltage regulation within a certain range can be achieved by controlling the thyristor's on / off state through the control of its conduction angle. This invention uses thyristors instead of ordinary diodes, which has the advantage of allowing the thyristors to be controlled by their conduction angle, thus providing the thyristor rectifier circuit with a certain voltage regulation capability.
[0030] The active filtering circuit includes a three-phase inverter composed of diodes, IGBTs, and DC capacitors, as well as a three-phase filtering inductor. The positive outputs of the first and second thyristor multi-pulse rectifier circuits are connected to the positive DC input of the three-phase inverter. The negative DC terminals of the first and second thyristor multi-pulse rectifier circuits are connected to the negative DC terminal of the three-phase inverter. The output of the three-phase inverter is connected to the secondary side of the multi-winding phase-shifting transformer through the three-phase filtering inductor.
[0031] In this embodiment, the three-phase inverter consists of two IGBTs per phase (a total of six diodes) and DC capacitors. The IGBTs can be controlled to turn on and off via a control drive signal. The active filter circuit can control the IGBTs to invert the DC voltage provided by the DC capacitors into AC current, which is then output to the filter winding via the three-phase filter inductor and transmitted to the primary winding, thereby achieving active compensation and filtering of the primary harmonic current.
[0032] like Figure 2 As shown, the control of the active filter circuit is achieved through the following steps: 1. Acquire the primary side three-phase AC current i a i b i c The system is then transformed sequentially into a two-phase stationary coordinate system and a two-phase rotating coordinate system. The component i of the primary side AC current before low-pass filtering in the two-phase rotating coordinate system is then analyzed. d i q Harmonic components i in the primary AC current are extracted by subtracting the components of the primary AC current in the two-phase rotating coordinate system after low-pass filtering. d,h iq,h The component i in the two-phase stationary coordinate system is obtained by inverse transformation and conversion to the two-phase stationary coordinate system. α,h i β,h 2. Acquire the AC voltage V output from the active filter circuit. a v b v c After transforming it sequentially to a two-phase stationary coordinate system and a two-phase rotating coordinate system, the DC component information v in the two-phase rotating coordinate system is extracted by low-pass filtering. d,dc v q,dc The DC capacitor voltage V dc Its reference value V dcref The difference between them is passed to the PI controller for calculation, and the result output by the PI controller is compared with the previously obtained DC component information v in the two-phase rotating coordinate system. d,dc v q,dc Multiplying these values yields the current reference value i corresponding to the DC voltage control. rd i rq It is then transformed to a two-phase stationary coordinate system through a two-phase rotational inverse transformation to obtain its component i in the two-phase stationary coordinate system. rα i rβ 3. The harmonic information of the primary side AC current in the two-phase stationary coordinate system obtained in steps 1 and 2 respectively is used to... α,h i β,h and DC voltage control current reference value information i rα i rβ As a reference value for the output current of the active filter circuit, and compared with the actual AC current value i of the active filter circuit output in the two-phase stationary coordinate system. Lα i Lβ The difference is calculated, and the result is multiplied by the filter circuit parameter coefficient L / T to obtain the reference value for the output voltage of the active filter circuit. This reference value is then compared with the output AC voltage V of the active filter circuit in the two-phase stationary coordinate system. α V β The difference is calculated, and the result, after inverse transformation to the three-phase stationary coordinate system, is used as the three-phase modulation voltage v' of the three-phase voltage source rectifier in the active filter circuit. a v' b v' c 4. Based on the three-phase modulation voltage v' obtained in step 3 a v' b v' c Calculate the zero-sequence voltage and superimpose it with the three-phase modulation voltage to obtain the final three-phase modulation voltage reference value v'. a,ref v' b,ref v' c,refFurthermore, the three-phase modulation voltage reference value is controlled by the PWM output to control the three-phase voltage source rectifier, thereby realizing the active filtering function.
[0033] The formula for calculating zero-sequence voltage is as follows:
[0034] v0 = -0.5(max(v a ′,v b ′,v c ′)+min(v a ′,v b ′,v c ′))
[0035] The filter circuit parameter coefficients are equal to L / T, where L is the three-phase filter inductance value and T is the sampling time.
[0036] The active filter circuit can also change the direction of the primary current by outputting current to the primary side, thus providing reverse power flow regulation, in the form of a load providing a stable DC voltage. That is, if the load can provide a stable DC voltage, by adjusting the control strategy of the active filter circuit, it can also change the direction of the primary current by outputting current to the primary side, providing reverse power flow to support the power grid.
[0037] The DC current output by the first thyristor multi-pulse rectifier circuit and the second thyristor multi-pulse rectifier circuit is connected in parallel through a balancing reactor to supply power to the load. The instantaneous voltage difference generated between the first thyristor multi-pulse rectifier circuit and the second thyristor multi-pulse rectifier circuit will be absorbed by the balancing reactor connected later and will not affect the load.
[0038] The hybrid multi-pulse rectifier transformer described in this invention has the following effects:
[0039] like Figure 3 As shown, the active filter circuit starts at 0.05s and begins to output harmonic compensation current. The output current of the active filter circuit in phase A begins to increase. It can be seen that while maintaining the phase A primary AC voltage and phase A primary AC current in phase (i.e., unity power factor), the quality of the phase A primary AC current is improved and the degree of current distortion is reduced by compensating for harmonics in the primary AC current. This verifies the active filtering capability of the hybrid multi-pulse rectifier transformer proposed in this invention. Between 0.15s and 0.25s, by adjusting the control strategy of the active filter circuit and changing the output current, while maintaining a basically constant DC voltage, the DC load power changes from positive to negative, achieving reverse load power output. This verifies that the active filter circuit of the hybrid multi-pulse rectifier transformer proposed in this invention can achieve reverse power flow.
Claims
1. A hybrid multi-pulse rectifier transformer with active filtering capability, characterized by, include: The circuit consists of a multi-winding phase-shifting transformer, an active filter circuit, a first thyristor multi-pulse rectifier circuit, and a second thyristor multi-pulse rectifier circuit. The primary side of the multi-winding phase-shifting transformer is connected to a three-phase power grid, while the secondary side is connected to two thyristor multi-pulse rectifier circuits and an active filter circuit. The two thyristor multi-pulse rectifier circuits rectify the AC power supplied by the secondary side of the multi-winding phase-shifting transformer into DC power, providing DC voltage to the load and the active filter circuit. The multi-winding phase-shifting transformer generates three sets of three-phase voltages. Two sets of three-phase voltages with different phases but the same amplitude, generated by phase shifting, are output to the two thyristor multi-pulse rectifier circuits respectively. The other set of three-phase voltages is not phase-shifted and is connected to the active filter circuit. The active filter circuit inverts the DC voltage into AC current and transmits it to the primary winding for active compensation and filtering of primary harmonic currents.
2. The hybrid multi-pulse rectifier transformer with active filtering capability according to claim 1, characterized in that, A multi-winding phase-shifting transformer includes three-phase windings. Each phase winding includes a primary winding, a first rectifier winding, a second rectifier winding, and a filter winding. The primary winding is used to connect to a three-phase AC power supply. The first rectifier winding is connected to the input of a first thyristor multi-pulse rectifier circuit on the secondary side. The second rectifier winding is connected to the input of a second thyristor multi-pulse rectifier circuit on the secondary side. The filter winding is connected to the output of an active filter circuit on the secondary side.
3. The hybrid multi-pulse rectifier transformer with active filtering capability according to claim 1, characterized in that, The active filtering circuit includes a three-phase inverter composed of diodes, IGBTs, and DC capacitors. The positive outputs of the first and second thyristor multi-pulse rectifier circuits are connected to the positive DC input of the three-phase inverter. The negative DC terminals of the first and second thyristor multi-pulse rectifier circuits are connected to the negative DC terminal of the three-phase inverter. The output of the three-phase inverter is connected to the secondary side of the multi-winding phase-shifting transformer.
4. The hybrid multi-pulse rectifier transformer with active filtering capability according to claim 3, characterized in that, The active filtering circuit also includes a three-phase filter inductor located between the output terminal of the three-phase inverter and the secondary winding, used to filter the AC current output by the three-phase inverter.
5. The hybrid multi-pulse rectifier transformer with active filtering capability according to claim 3, characterized in that, The DC voltage provided by the DC capacitor is converted into AC current by controlling the IGBT. The AC current is then filtered by the three-phase filter inductor and transmitted to the primary winding through the secondary winding.
6. The hybrid multi-pulse rectifier transformer with active filtering capability according to claim 1, characterized in that, The hybrid multi-pulse rectifier transformer also includes a current-limiting diode. The positive outputs of the first and second thyristor multi-pulse rectifier circuits are connected to the positive DC input of the active filter circuit through the current-limiting diode. The negative outputs of the first and second thyristor multi-pulse rectifier circuits are connected to the negative DC input of the active filter circuit.
7. The hybrid multi-pulse rectifier transformer with active filtering capability according to claim 1, characterized in that, The hybrid multi-pulse rectifier transformer also includes a balancing reactor. The DC current output by the first thyristor multi-pulse rectifier circuit and the second thyristor multi-pulse rectifier circuit is connected in parallel through the balancing reactor and then supplies power to the load.
8. The hybrid multi-pulse rectifier transformer with active filtering capability according to claim 1, characterized in that, If the load can provide a stable DC voltage, by adjusting the control strategy of the active filter circuit, the active filter circuit also has the function of changing the current direction of the primary side by outputting current to the primary side, and providing reverse power flow to support the power grid.
9. The hybrid multi-pulse rectifier transformer with active filtering capability according to claim 1, characterized in that, The first thyristor multi-pulse rectifier circuit and the second thyristor multi-pulse rectifier circuit are both composed of controllable thyristors, and the multi-pulse rectification and output voltage regulation functions are realized by controlling the conduction angle of the thyristors.
10. A method of active filtering of a hybrid multi-pulse rectifier transformer according to any one of claims 1 to 9, characterized in that, The active compensation filtering of the primary side harmonic current is realized by controlling the active filter circuit, including the following steps: The active compensation filtering of the primary side harmonic current is realized by controlling the active filter circuit, including the following steps: (1) The primary side three-phase AC current i a i b i c The system is sequentially transformed into a two-phase stationary coordinate system and then into a two-phase rotating coordinate system. The component i of the primary side AC current before low-pass filtering in the two-phase rotating coordinate system is then analyzed. d i q The harmonic components i in the primary AC current are extracted by subtracting the low-pass filtered component. d,h i q,h And its component i in the two-phase stationary coordinate system is obtained by inverse two-phase rotation transformation. α,h i β,h ; (2) The AC voltage v output by the active filter circuit a v b v c The system is sequentially transformed to a two-phase stationary coordinate system and then to a two-phase rotating coordinate system. The DC component information (v) in the two-phase rotating coordinate system is then extracted using a low-pass filter. d,dc v q,dc The DC capacitor voltage V dc Its reference value V dcref The difference between them is passed to the PI controller for calculation, and the output of the PI controller is compared with the previously obtained v. d,dc v q,dc Multiplying them together yields the current reference value i corresponding to DC voltage control. rd i rq And its component i in the two-phase stationary coordinate system is obtained by inverse two-phase rotation transformation. rα i rβ ; (3) The primary side AC current harmonics i obtained in steps (1) and (2) in the two-phase stationary coordinate system respectively α,h i β,h and DC voltage control current reference value i rα i rβ As a reference value for the output current of the active filter circuit, and compared with the output AC current i of the active filter circuit transformed into a two-phase stationary coordinate system. Lα i Lβ The difference is calculated, and the result is multiplied by the filter circuit coefficient to obtain the reference value for the output voltage of the active filter circuit. This reference value is then compared with the output AC voltage V of the active filter circuit in the two-phase stationary coordinate system. α V β The difference is calculated, and the result, after inverse transformation to the three-phase stationary coordinate system, is used as the three-phase modulation voltage v' of the three-phase voltage source rectifier in the active filter circuit. a 、v'b、v' c ; (4) The three-phase modulation voltage v' a , v' b , v' c The zero sequence voltage is calculated, and the obtained zero sequence voltage is superimposed with the three-phase modulation voltage to obtain the final three-phase modulation voltage reference value v' a,ref , v' c,ref The three-phase modulation voltage reference value is further output through PWM to control the three-phase voltage source rectifier, thereby realizing the active filtering function.